Paradigm changes in freshwater aquaculture practices in China: Moving towards achieving environmental integrity and sustainability

Contribution of fisheries and aquaculture to global food security is linked to increased fish consumption. Projections indicate that an additional 30–40 million tonnes of fish will be required by 2030. China leads global aquaculture production accounting for 60% in volume and 45% in value. Many changes in the Chinese aquaculture sector are occurring to strive towards attaining environmental integrity and prudent use of resources. We focus on changes introduced in freshwater aquaculture developments in China, the main source of food fish supplies. We bring forth evidence in support of the contention that Chinese freshwater aquaculture sector has introduced major paradigm changes such as prohibition of fertilisation in large water bodies, introduction of stringent standards on nutrients in effluent and encouragement of practices that strip nutrients among others, which will facilitate long-term sustainability of the sector.     

From aquaculture goals to real social and ecological impacts: carp introduction in rural Central Mexico

Aquaculture has been seen as a solution to food/protein availability in rural populations of poor countries. It is mainly based on exotic species, that produce changes in host system dynamics once introduced. Aquaculture not only changes the ecology of freshwater systems, but can also lead to modification of social relations. Until now, aquaculture programs have not been adequately analyzed no questioned enough. We evaluate both ecological effects and local social benefits of common carp aquaculture programs in shallow ponds of rural areas, using a municipality in Central Mexico as a case study. Using an "environmental entitlements" approach, our findings suggest that: i) carp aquaculture increases water turbidity and depletes native species reducing the poor people's access to them; ii) aquaculture mainly benefits pond owners rather than poor peasants. This mainly results from changes in fishing rights. We conclude that aquaculture policy goals and assumptions of benefits should be reviewed, if the negative ecological effects are to be decreased and conditions for people in rural areas are to be improved.     

Aquaculture expansion in Brazilian freshwaters against the Aichi Biodiversity Targets

The Convention on Biological Diversity proposed the Aichi Biodiversity Targets to improve conservation policies and to balance economic development, social welfare, and the maintenance of biodiversity/ecosystem services. Brazil is a signatory of the Aichi Biodiversity Targets and is the most diverse country in terms of freshwater fish, but its national policies have supported the development of unsustainable commercial and ornamental aquaculture, which has led to serious disturbances to inland ecosystems and natural resources. We analyzed the development of Brazilian aquaculture to show how current aquaculture expansion conflicts with all 20 Aichi Targets. This case suggests that Brazil and many other megadiverse developing countries will not meet international conservation targets, stressing the need for new strategies, such as the environmental management system, to improve biodiversity conservation.     

可用于水体污染控制的氨氮转化菌筛选及部分降解特性的实验研究

从南京禄口水产养殖基地淡水鱼塘取淤泥作为分离菌株的土源,采用选择性富集培养法,从中分离到能以硫酸铵为氮源的菌株7株,对7个菌株进行氨氮降解实验,它们氨氮转化率分别为14.8%、19.7%、53.4%、94.2%、29.1%、63.5%和41.7%,其中AN-4菌株的转化率最高且生长良好。通过AN-4菌株16S rRNA基因序列分析以及生理生化方法,鉴定此菌株为克雷伯氏菌属(Klebsiellasp.)。对菌株AN-4转化氨氮的特性及温度、pH值、氨氮初始浓度和菌株接种量对其氨氮转化率的影响研究,结果表明,菌株AN-4降解氨氮的最适条件为:温度为30℃和pH值为8.0;当氨氮初始浓度为30mg/L时,AN-4菌株在24 h内的氨氮降解率可达85%以上,且能耐受高达200 mg/L的氨氮浓度;AN-4活化菌液浓度为108cfu/mL,当接种量为3×106cfu/mL时,AN-4菌株在24 h内的氨氮降解率为87.75%。综合上述结果,符合淡水养殖水环境条件,说明AN-4菌株适合在水产养殖中应用,为将菌株AN-4应用于水产养殖环境修复提供了理论依据。     

Trophic relationships and health risk assessments of trace metals in the aquaculture pond ecosystem of Pearl River Delta,China

Cadmium, lead, zinc, Chromium, copper, nickel and manganese in sediments and in aquatic organisms were collected from the aquaculture pond ecosystem of the Pearl River Delta (PRD), China and analyzed to evaluate bioaccumulation and trophic transfer in food chains, as well as the potential health risk of exposure to the Hong Kong residents via dietary intake of these aquatic products. The results revealed that based on the biota–sediment accumulation factor, omnivorous fish and zooplankton accumulated more trace metals from sediment than carnivorous fish. Concentrations of seven trace metals in aquaculture pond of PRD significantly decreased with increasing trophic levels, showing that these trace metals were trophically diluted in predatory and omnivorous food chains. The hazard index values of all fish species were smaller than 1 for adults and children, indicating there was no health risk from the multiple metals via ingestion of the freshwater fish for the inhabitants.     

Dissolved oxygen and dietary phosphorus modulate utilization and effluent partitioning of phosphorus in rainbow trout (Oncorhynchus mykiss) aquaculture

Phosphorus (P) is the limiting nutrient in freshwater primary production, and excessive levels cause premature eutrophication. P levels in aquaculture effluents are now tightly regulated. Increasing our understanding of waste P partitioning into soluble, particulate, and settleable fractions is important in the management of effluent P. When water supply is limited, dissolved oxygen concentration (DO) decreases below the optimum levels. Therefore, we studied effects of DO (6 and 10mg/L) and dietary P (0.7 and 1.0% P) on rainbow trout growth, P utilization, and effluent P partitioning. Biomass increased by 40% after 3 weeks. DO at 10mg/L significantly increased fish growth and feed efficiency, and increased the amount of P in the soluble fraction of the effluent. Soluble effluent P was greater in fish fed 1.0% P. DO increases fish growth and modulates P partitioning in aquaculture effluent.     

Evaluation on subcellular partitioning and biodynamics of pulse copper toxicity in tilapia reveals impacts of a major environmental disturbance

Fluctuation exposure of trace metal copper (Cu) is ubiquitous in aquatic environments. The purpose of this study was to investigate the impacts of chronically pulsed exposure on biodynamics and subcellular partitioning of Cu in freshwater tilapia (Oreochromis mossambicus). Long-term 28-day pulsed Cu exposure experiments were performed to explore subcellular partitioning and toxicokinetics/toxicodynamics of Cu in tilapia. Subcellular partitioning linking with a metal influx scheme was used to estimate detoxification and elimination rates. A biotic ligand model-based damage assessment model was used to take into account environmental effects and biological mechanisms of Cu toxicity. We demonstrated that the probability causing 50% of susceptibility risk in response to pulse Cu exposure in generic Taiwan aquaculture ponds was ~33% of Cu in adverse physiologically associated, metabolically active pool, implicating no significant susceptibility risk for tilapia. We suggest that our integrated ecotoxicological models linking chronic exposure measurements with subcellular partitioning can facilitate a risk assessment framework that provides a predictive tool for preventive susceptibility reduction strategies for freshwater fish exposed to pulse metal stressors.     

Arsenic contamination in the freshwater fish ponds of Pearl River Delta: bioaccumulation and health risk assessment

This study investigated the extent of arsenic (As) contamination in five common species of freshwater fish (northern snakehead [Channa argus], mandrarin fish [Siniperca chuatsi], largemouth bass [Lepomis macrochirous], bighead carp [Aristichthys nobilis] and grass carp [Ctenopharyngodon idellus]) and their associated fish pond sediments collected from 18 freshwater fish ponds around the Pearl River Delta (PRD). The total As concentrations detected in fish muscle and sediment in freshwater ponds around the PRD were 0.05–3.01 mg?kg^?1 wet weight (w. wt) and 8.41–22.76 mg?kg^?1 dry weight (d. wt), respectively. In addition, the As content was positively correlated (p?<?0.05) to total organic carbon (TOC) contents in sediments. Biota sediment accumulation factor (BSAF) showed that omnivorous fish and zooplankton accumulated higher concentrations of heavy metals from the sediment than carnivorous fish. In addition, feeding habits of fish also influence As accumulation in different fish species. In this study, two typical food chains of the aquaculture ponds were selected for investigation: (1) omnivorous food chain (zooplankton, grass carp and bighead carp) and (2) predatory food chain (zooplankton, mud carp and mandarin fish). Significant linear relationships were obtained between log As and δ ¹⁵N. The slope of the regression (?0.066 and ?0.078) of the log transformed As concentrations and δ ¹⁵N values, as biomagnifications power, indicated there was no magnification or diminution of As from lower trophic levels (zooplankton) to fish in the aquaculture ponds. Consumption of largemouth bass, northern snakehead and bighead carp might impose health risks of Hong Kong residents consuming these fish to the local population, due to the fact that its cancer risk (CR) value exceeded the upper limit of the acceptable risk levels (10^?4) stipulated by the USEPA.     

How do land-based salmonid farms affect stream ecology?

Increasing research is highlighting the fact that streams provide crucial ecosystem services through the biogeochemical and ecological processes they sustain. Freshwater land-based salmonid farms commonly discharge their effluents into low order, headwater streams, partly due to the fact that adequate freshwater resources for production are commonly found in undisturbed areas. We review the effects of salmonid farm effluents on different biological components of stream ecosystems. Relevant considerations related to the temporal and spatial scales of effluent discharge and ecological effects are discussed. These highlight the need to characterize the patterns of stressor discharge when assessing environmental impacts and designing ecological effects studies. The potential role of multiple stressors in disrupting ecosystem structure and function is discussed with an emphasis on aquaculture veterinary medicines. Further research on the effects of veterinary medicines using relevant exposure scenarios would significantly contribute to our understanding of their impact in relation to other effluent stressors.     

Effects of Bacillus subtilis on the growth,colony maintenance,and attached bacterial community composition of colonial cyanobacteria

In freshwater aquaculture ponds, application of algicidal Bacillus is a promising way in the control of cyanobacterial blooms. To best understand Bacillus algicidal characters and mechanisms in the field, different-sized colonial cyanobacteria were isolated from an aquaculture pond, and the effects of B. subtilis on their growth, colony maintenance, and colony-attached bacterial community composition were investigated. The results showed that B. subtilis could inhibit the growth of colonial cyanobacteria. Bigger-sized colonies isolated from the field could spontaneously disintegrate into smaller-sized colonies in the laboratory. Algicidal B. subtilis could accelerate the disintegration of colonies and decrease colony size. B. subtilis not only decreased the colony-attached bacterial community diversity but also changed its composition. B. subtilis increased the relative abundances of some attached bacterial genera, including Pseudomonas, Shewanella, Bacillus, Shinella, Rhizobium, and Ensifer. These bacteria with algicidal, microcystin-degrading, and flocculating activities might be an important contributor to algicidal effects of B. subtilis on colonial cyanobacteria.

     

A comparison of microplastic contamination in freshwater fish from natural and farmed sources

Contamination of aquatic systems mainly by urbanization and poor sanitation, deficient or lack of wastewater treatments, dumping of solid residues, and run off has led to the presence of particles, including manmade polymers, in tissues of many marine and freshwater species. In this study, the prevalence of microplastics (MPs) in freshwater fish from farmed and natural sources was investigated. Oreochromis niloticus from aquaculture farms in the Huila region in Colombia, and two local species (Prochilodus magdalenae and Pimelodus grosskopfii), naturally present in surface waters were sampled. Of the particles identified, fragments were the predominant type in the three tissue types (stomach, gill, and flesh) derived from farmed and natural fishes. MicroFT-IR spectroscopy was conducted on 208 randomly selected samples, with 22% of particles identified as MPs based on spectra with a match rate ≥ 70%. A total of 53% of identified particles corresponded to cellophane/cellulose, the most abundant particle found in all fish. Not all fish contained MPs: 44% of Oreochromis farmed fish contained MPs, while 75% of natural source fish contained MPs in any of its tissues. Overall, polyethylene terephthalate (PET), polyester (PES), and polyethylene (PE) were the prevalent MPs found in the freshwater fish. A broader variety of polymer types was observed in farmed fish. The edible flesh part of fish presented the lower prevalence of MPs compared to gill and stomach (gut), with gut displaying a higher frequency and diversity of MPs. This preliminary study suggests that the incidence and type of MPs varies in farmed verses natural fish sources as well as across different tissue types, with significantly less detected within the edible flesh tissues compared with stomach and gill tissues.

     

哑铃湾网箱养殖可持续容量研究

在相关养殖容量研究的基础上,提出了养殖环境容量和可持续养殖容量的概念和内涵.以哑铃湾网箱养殖为例,建立了考虑时间累积效应后的养殖环境容量和考虑了社会、经济和环境综合效益后的可持续养殖容量计算模型.估算了在10年时段内哑铃湾网箱养殖环境容量和可持续养殖容量.结果表明,哑铃湾网箱养殖最优环境容量为每年4.11万箱,可持续养殖容量为每年3.45万箱.     

Passing the Panda Standard: A TAD Off the Mark?

Tilapia, a tropical freshwater fish native to Africa, is an increasingly important global food commodity. The World Wide Fund for Nature (WWF), a major environmental nongovernmental organization, has established stakeholder dialogues to formulate farm certification standards that promote “responsible” culture practices. As a preface to its “tilapia aquaculture dialogue,” the WWF for Nature commissioned a review of potential certification issues, later published as a peer-reviewed article. This article contends that both the review and the draft certification standards subsequently developed fail to adequately integrate critical factors governing the relative sustainability of tilapia production and thereby miss more significant issues related to resource-use efficiency and the appropriation of ecosystem space and services. This raises a distinct possibility that subsequent certification will promote intensive systems of tilapia production that are far less ecologically benign than existing widely practiced semi-intensive alternatives. Given the likely future significance of this emergent standard, it is contended that a more holistic approach to certification is essential.     

水产养殖自身污染及其生物修复技术

介绍了生物修复的概念、水产养殖存在的自身污染问题及其主要生物修复技术.营养物污染、药物污染和底泥富集污染是水产养殖存在的主要自身污染问题;微生物修复、水生植物修复和水生动物修复是污染养殖水域生物修复的3种主要形式;微生物的有效性、生物入侵、二次污染、修复生物的季节性和非水生植物的利用等方面是实施生物修复应注意的主要方面.最后指出,推行清洁生产、实行生态养殖是水产养殖业可持续发展的出路.     

Environmental impact of aquaculture and countermeasures to aquaculture pollution in China

GOAL, SCOPE AND BACKGROUND: Aquaculture activities are well known to be the major contributor to the increasing level of organic waste and toxic compound in the aquaculture industry. Along with the development of intensive aquaculture in China, concerns are evoked about the possible effects of ever-increasing aquaculture waste both on productivity inside the aquaculture system and on the ambient aquatic ecosystem. Therefore, it is apparent that appropriate waste treatment processes are needed for sustaining aquaculture development. This review aims at identifying the current status of aquaculture and aquaculture waste production in China. MAIN FEATURES: China is the world's largest fishery nation in terms of total seafood production volume, a position it has maintained continuously since 1990. Freshwater aquaculture is a major part of the Chinese fishery industry. Marine aquaculture in China consists of both land-based and offshore aquaculture, with the latter mostly operated in shallow seas, mud flats and protected bays. The environmental impacts of aquaculture are also striking. RESULTS: Case studies on pollution hot spots caused by aquaculture have been introduced. The quality and quantity of waste from aquaculture depends mainly on culture system characteristics and the choice of species, but also on feed quality and management. Wastewater without treatment, if continuously discharged into the aquatic environment, could result in remarkable elevation of the total organic matter contents and cause considerable economy lost. Waste treatments can be mainly classified into three categories: physical, chemical and biological methods. DISCUSSION: The environmental impacts of different aquaculture species are not the same. New waste treatments are introduced as references for the potential development of the waste treatment system in China. The most appropriate waste treatment system for each site should be selected according to the sites' conditions and financial status as well as by weighing the advantages and disadvantages of each system. Strategies and perspectives for sustainable aquaculture development are proposed, with the emphasis on environmental protection. CONCLUSIONS: Negative effects of waste from aquaculture to aquatic environment are increasingly recognized, though they were just a small proportion to land-based pollutants. Properly planned use of aquaculture waste alleviates water pollution problems and not only conserves valuable water resources but also takes advantage of the nutrients contained in effluent. It is highly demanding to develop sustainable aquaculture which keeps stocking density and pollution loadings under environmental capacity. RECOMMENDATIONS AND PERSPECTIVES: The traditional procedures for aquaculture waste treatment, mainly based on physical and chemical means, should be overcome by more site-specific approaches, taking into account the characteristics and resistibility of the aquatic environment. Further research needs to improve or optimize the current methods of wastewater treatment and reuse. Proposed new treatment technology should evaluate their feasibility at a larger scale for practical application.     

水产养殖废水处理技术及应用

主要综述了国内外水产养殖废水的物理化学处理和生物处理 2方面的技术 ,并总结了水产养殖废水循环使用的水处理工艺流程和生物工程在水产养殖废水处理中的应用 ,表明了水产养殖废水的综合利用和无害化排放技术为今后发展方向。     

ESPR subject area 5 ‘Environmental Microbiology, (Bio)Technologies, Health Issues’

Goal, Scope and Background  Aquaculture activities are well known to be the major contributor to the increasing level of organic waste and toxic compounds in the aquaculture industry. Along with the development of intensive aquaculture in China, concerns are evoked about the possible effects of everincreasing aquaculture waste both on productivity inside the aquaculture system and on the ambient aquatic ecosystem. Therefore, it is apparent that appropriate waste treatment processes are needed for sustaining aquaculture development. This review aims at identifying the current status of aquaculture and aquaculture waste production in China. Main Features  China is the world’s largest fishery nation in terms of total seafood production volume, a position it has maintained continuously since 1990. Freshwater aquaculture is a major part of the Chinese fishery industry. Marine aquaculture in China consists of both land-based and offshore aquaculture, with the latter mostly operated in shallow seas, mud flats and protected bays. The environmental impacts of aquaculture are also striking. Results  Case studies on pollution hot spots caused by aquaculture have been introduced. The quality and quantity of waste from aquaculture depends mainly on culture system characteristics and the choice of species, but also on feed quality and management. Wastewater without treatment, if continuously discharged into the aquatic environment, could result in remarkable elevation of the total organic matter contents and cause considerable economy lost. Waste treatments can be mainly classified into three categories: physical, chemical and biological methods. Discussion  The environmental impacts of different aquaculture species are not the same. New waste treatments are introduced as references for the potential development of the waste treatment system in China. The most appropriate waste treatment system for each site should be selected according to the sites’ conditions and financial status as well as by weighing the advantages and disadvantages of each system. Strategies and perspectives for sustainable aquaculture development are proposed, with the emphasis on environmental protection. Conclusions  Negative effects of waste from aquaculture to aquatic environment are increasingly recognized, though they were just a small proportion to land-based pollutants. Properly planned use of aquaculture waste alleviates water pollution problems and not only conserves valuable water resources but also takes advantage of the nutrients contained in effluent. It is highly demanding to develop sustainable aquaculture which keeps stocking density and pollution loadings under environmental capacity. Recommendations and Perspectives  The traditional procedures for aquaculture waste treatment, mainly based on physical and chemical means, should be overcome by more site-specific approaches, taking into account the characteristics and resistibility of the aquatic environment. Further research needs to improve or optimize the current methods of wastewater treatment and reuse. Proposed new treatment technology should evaluate their feasibility at a larger scale for practical application. ESS-Submission Editor: Dr. Ding Wang (wangd@ihb.ac.cn)     

水产养殖自身污染及其生物修复技术

介绍了生物修复的概念、水产养殖存在的自身污染问题及其主要生物修复技术。营养物污染、药物污染和底泥富集污染是水产养殖存在的主要自身污染问题；微生物修复、水生植物修复和水生动物修复是污染养殖水域生物修复的3种主要形式；微生物的有效性、生物入侵、二次污染、修复生物的季节性和非水生植物的利用等方面是实施生物修复应注意的主要方面。最后指出，推行清洁生产、实行生态养殖是水产养殖业可持续发展的出路。     

Why are Prices in Wild Catch and Aquaculture Industries so Different?

Through a comparative analysis of prices in capture fisheries and aquaculture sectors, the objectives of this paper are a) to investigate three the trends in prices of forage catches to feed the aquaculture species, b) to analyze the amount of fish species need to feed aquaculture species in order to assess the level of efficiency in resource use, and c) to examine the degree of economic concentration either in wild-catch industry and aquaculture sectors. The results show that prices of cultivated species are higher than prices of the same species when harvested from the sea. We explain this fact by the interplay of three forces. First, the amount of wild fish to feed aquaculture species continues to improve over time. Second, the pressure of fishing activities has not been reduced since catches of most forage fishes are declining, which induce higher prices of capture species that feed aquaculture production. Third, the level of seafood market concentration is significantly higher in aquaculture than in wild catches, which generates higher prices in aquaculture.     

Toxicokinetics/toxicodynamics links bioavailability for assessing arsenic uptake and toxicity in three aquaculture species

The purpose of this study was to link toxicokinetics/toxicodynamics (TK/TD) and bioavailability-based metal uptake kinetics to assess arsenic (As) uptake and bioaccumulation in three common farmed species of tilapia (Oreochromis mossambicus), milkfish (Chanos chanos), and freshwater clam (Corbicula fluminea). We developed a mechanistic framework by linking damage assessment model (DAM) and bioavailability-based Michaelis?CMenten model for describing TK/TD and As uptake mechanisms. The proposed model was verified with published acute toxicity data. The estimated TK/TD parameters were used to simulate the relationship between bioavailable As uptake and susceptibility probability. The As toxicity was also evaluated based on a constructed elimination?Crecovery scheme. Absorption rate constants were estimated to be 0.025, 0.016, and 0.175?mL g^?1 h^?1 and As uptake rate constant estimates were 22.875, 63.125, and 788.318?ng g^?1 h^?1 for tilapia, milkfish, and freshwater clam, respectively. Here we showed that a potential trade-off between capacities of As elimination and damage recovery was found among three farmed species. Moreover, the susceptibility probability can also be estimated by the elimination?Crecovery relations. This study suggested that bioavailability-based uptake kinetics and TK/TD-based DAM could be integrated for assessing metal uptake and toxicity in aquatic organisms. This study is useful to quantitatively assess the complex environmental behavior of metal uptake and implicate to risk assessment of metals in aquaculture systems.